re: fuel usage calculation
16 nov 2000
scott murray wrote:
>i am trying to determine if running my gas (propane) furnace and heating
>the entire house 2800sqft of which we live in only half... or using
>suplemential heaters gas or electric in the rooms we use is less expensive
it's probably less expensive (by up to 50%) to only heat half of the house,
if the supplemental heaters are gas. otoh, electricity costs about 3x more
per btu than gas, so supplemental electric heaters might be more expensive.
>what i need to know is how much fuel is my furnace using: is there
>a formula for btu x fuel price x hours used...
your propane dealer should be able to tell you the price and weight and
fuel heating value in btu/gallon. propane has a "lower heating value" of
19,397 btu/lb (93,500 btu per 4.8 pound gallon?) when the water vapor from
combustion leaves the house, and a "higher heating value" of 21,669 btu/lb
when the water vapor condenses inside the house, as it would do with an
unvented heater. the 12% difference is enough to evaporate about 2.4 pounds
of water per pound of propane, so you might not need a humidifier in winter
(unless you were ken h :-) with unvented heaters...